Circuit maker and breaker



0d. 15, 1929. 5, DENISON 1,732,182

CIRCUIT MAKER AND BREAKER Filed June 2'7, 1925 2 Sheets-Sheet l Oct. 15,1929. s, DENISQN 1,732,182

CIRCUIT MAKER AND BREAKER Filed June 27, 1925 2 Sheets-Sheet 2 8 Pow!Zws SUPPLY CIRCUIT 9 RaoM Tum-105141 fi C MBLLiT/O/V THERHOsTAT BREAKER3 54 47 52 a 62 '6 J 0 1 20'- 70 77 53 (65 69 74 y --MOTOR CmU/T a5 84*5 35 1; I/ E 92 k 0 86 9/ an VALVE.

/770/?MEYS Patented Oct. .15, 1929 UNITED STATES PATENT OFFICE FREDERICKS. DENISON, F MINNEAPOLIS, MINNESOTA, ASSIGNOB, BY MESNE ASSIGN- MENTS,TO MINNEAPOLIS HONEYWELL REGULATOR COMPANY, OF MINNEAPOLIS, MINNESOTA, ACORPORATION OF DELAWARE cmcurr MAKER AND BREAKER This invention relatesto new and useful improvements in the methods of and apparatus forcontrolling combustion mechanism and more particularly relates to suchmocha-- nisms having a fuel feeding apparatus which is electricallycontrolled. It is common especially in the art of oil-burners to employthermostatically. controlled burners which control not only effects thestarting and stopping of the burner operation and fuel feeding but alsoignition therefor. It is highly advantageous to employ a safety meanswhich will automatically stop the fuel feeding upon failure ofcombustion of the fed 11; fuel whether such failure of combustion occursinitially or intermediately during the fuel feeding. In this novelinvention, a safetymeans is provided which is automatically operableupon starting of the fuel feed- 2o ing to stop the same after apredetermined interval. This novel process and apparatus also includestheuse of the combustion'of the fuel as a control medium to render thesa/fety means ino erative before completion of its stopping unction and,further, this control medium may also be used to stop operation of'anignition means.

Further, this process provides the control-' ling of an electricallyoperated fuel feeding apparatus which consists in closing a circuit tothe fuel feeding means to operate the same,

providing an ignition means for the feed fuel, causing the safety meansupon closure of the circuit to start functioning automatically to stopthe fuel feeding after a predetermined interval, using the heat ofcombustion of the fuel as a control medium 'to render the safety meansinoperative before completion of its function, and using the failure ofcombustion while said circuit is closed as a control medium to permitsaid safety means to function to stop the fuel feeding after apredetermined interval. The object therefore of this invention is toprovide a method of, and apparatus for, controlling combustionmechanisms. i

Other objects of the invention will more fully appear from the followingdescription anckthe accompanying drawings and will be pointed out in theannexed claims.

In the drawings there has been disclosed a structure designed to carryoutthe various objects of the invention, but it is to be understood thatthe invention is not confined to the exact features shown as variouschanges ma be made within the scope of the claims whic follow.

In the drawings: I

Figure 1 is a view in side elevation of a thermostatic member mounted sothat its thermostatic element is responsive to the heat of combustion,the mounting being shown in section;

Figure 2 is a cross-sectional view on the line 2-2 of Figure 1;

Figure 3 is a similar view on the line 33 of Figure 1;

Figure 4 is a view of the disc and movable parts in the intermediatepositions assumed when the two of the contacts are diseng'aged andtwoare still engaged;

F i are 5 is a view similar to the foregoing but s owing all contactsdisenga ed; and

Figure 6 is a wiring diagram 0 the apparatus embodying the invention.

This novel process and apparatus may be explained and illustrated inconjunction with the relay control mechanism forming the subject-matterof the prior pending application of the inventor hereof Serial -Number722,586, filed June 26, 1924. Such mecha nism, its construction andoperation will be first described and then-the automatic cutout orsafety switch and thereafter the device which is adapted to renderinoperative the safety switch when the device is affecte by the heat ofcombustion.

The fuel feeding device may include an electric motor 7 which is adaptedto operate a blower to jet the fuel, such as oil, to the In the formhere disclosed the thermostat 12 formed of a bar of suitable metal whichis an electric conductor. As the mechanism is preferably mounted in anupright position, the blade 12 depends from the thermo-bar 11. Thisring-like bar is mounted, as is usual in insulated relation.

Two terminals are supported adjacent the bar 11 and are here indicatedas terminally pointed contacts 13 and 14. The contact 13 is electricallyconnected to the wire 15 and the contact 14 is so connected to the wire16.

A, single control circuit is preferably used and it may be closed acrossthe contacts 13-14 and, in the form shown, the circuitclosing meansconsists of a pair of members adapted to be successively engaged withtheir respective contacts. The relatively stiff blade 12 is carried bythe thermo-bar 11 and is adapted to engage the contact 13 in order toform an electrical connection therewith. A second blade 17 is alsocarried by the thermobar 11 by means of its welding to the blade 12. Theblades 12 and 17 are so arranged that they terminally diverge and eachbears a contact tip 18. The contact tip of the flexible blade 17 isadapted to engage the end of the lower contact 14. This flexible blade17 is also provided with an aperture 19 so that the other contact 13 mayfreely be passed therethrough, the resultant air gap providingsufficient insulation between the contact 13 and the flexible blade 17.This flexible blade is also desirably provided with a reinforcing orbacking plate 21. The upper ends of the backing plate, the flexibleblade 17 and the relatively stiff blade 12 are welded together topresent a substantially unitary structure in electrical connection atthat end. The plate 21 and blade 12 are both of relatively still metaland are disposed in terminally diverging relation, the flexible bladebeing interposed so that its flexibility permits'movement of its majorportion between the backing plate and blade 12. It may also be notedthat the backing plate is provided with an aperture similar to the blade17 for the same purpose. In addition to the thermostatic circuit wires15 and 16, which are respectively connected to the contacts 13 and 14, asupplemental wire' 22 is electrically connected to the thermo-bar 11and, hence to the blades 12 and 17. f

The switch forming the subject matter of the previously cited pendingapplication may next be described in conjunction with its connections.The switch is preferably borne by a panel usually mounted in a verticalpositionr An electro-magnetic coil 23 is mounted thereon to attract,when energized, an

armature 24 having a weighted portion 25 and mounted upon a pivot pin26. This armature lever has an arm 27 projecting beyond the pin 26 toengage and normally uped upon the pivot posts 34 and the counterweight28 normally tends to retain each tip 31 in contact with the respectiveterminal contacts 35 of the lead wires 32 and 33, the opening movementbeing limited by the adjustable screw 36. Upon closure of these switcharms 29, electrical energy passes from the line 8 to the lead wire 33 tocontact 35 to switcharm contact 31, through the switch arm to post 34and, by wire 37 to the device to be energized such as the burner motor7, and thence returns by the wire 38 to the other post 34, other switcharm 29, contacts 3135, wire 32 to the other power line 9. j

Thus, the counterweight 28 constantly exerts a gravitational forcetending tohold the switch arms 29 in closed position. But, the armatureweight 25 which exerts a greater force overcomes the force of thecounterweight 28 and normally holds the switch-arms in open position.However, upon 'energizauntil the electromagnet is de-energized where- Iby the weight 25 may indirectly open the switch-arms.

The energization and de-energization of the electromagnet is efl'ectedby means of the thermostatic mechanism above-mentioned. The twoswitch-arms 29 are conventionally represented as tied together by thebar 39 because they function as a unit in pivotal movements upon theirposts 34. The electromagnet 23 is in series with the wire 41 which isterminally connected to the secondary side of a transformer 42'which hasits primary constantly energized by its' shunt circuits 4344 from thelines 32-33. The Wire 16 leads from the other end of the secondary ofthis transformer to the thermostat c'ontact 14.

In the wiring diagram, the parts are represented in the positionsoccupied when the blower-motor 7 is shut oif and the thermostat, usuallypositioned in th room or place to be heated, is warm enou to hold theblades from circuit-closing position so'that the electromagnet circuitis open at the posts 13 and 14. As the thermo-bar cools, the blades 12and 17 and the backingplate 21 move toward the contacts 13 and 14. Owingto the diventhe other blade 12 is spaced from its contact- 13. Theelectromagnet circuit thus remains open, being broken at the posts.Further movement of the cooling thermo-bar causes engagement of thestiif'blade 12 with its contact 13. The backing plate maintains itsspaced relation from the blade 12 whilethe blade 17 flexibly remains incontact with its contact 14; Thus, the contacts are successively madeand the electromagnet circuit is closed across the contact screws sothat the electromagnet is energized, its armature weight 25 is raisedwhich permits the weight 28 to drop and thus to move the switch armsinto position closing the main line circuit to the motor. Beginning withcontact 13 this circuit is as follows: wire 15, post 69, wire 84, coil92, wire 86, wire 87, secondary element of the transformer 88, wire 89,binding post 68, wire 67, contact 64, post 72, to post 71, wire 41, topost 34, wire 41, coil 23, wire 41 to secondary side of transformer 42,wire 16, post 103, conductor elements 101, 99, 97, post 98, wire 16,post 14. One of theswitch arms carries a short arm 45 which iselectrically connected to thewire 41 leading from the electromagnet tothe contact 13 through the combustion-affected thermo-switch as will belater described. However, this arm 25 is adapted. when the switch-armsare closed, to effect electrical engagement with the relatively fixedcontact 46 which is connected by the wire 22 to the room thermo-bar 11.Thus, when the switch-arms are moved to circuitclosing position, the arm45 cuts out the portion of the wire 41 connecting the post 34and itsnormal circuit-continuation viathe wire 15 to the post 13 of the roomthermostat. Th is condition obtains so long as the electro-magnet 23remains energized and any accidental break in the current from the powerline will de-energize the electromagnet and cause the motor circuit tobe opened by force of gravity acting through the weight 25 which isheavier than the counterweight 28 and is therefore able to open theswitch-arms 29 againstthe pull of the counterweight 28.

However, disregarding such abnormal or accidental condition, themotor-switch-arms may be caused to be opened by movement of thethermo-bar 11 when it becomes heated and successively moves the blades12 .and 17 from their contacts. The circuit .is not interrupted untilthe thermo-bar has moved a predetermined distance fr'om the contacts.Such alag in the breaking is provided by the use of the relatively stiffand flexible contact blades and the supplemental connection for thethermo-bar and blades. Thus, as the heating thermo-barmoves from thecontacts, the stiff blade 12 is first disengaged from its post 13 and insuch position, the contact 13 and its connections via wire 15 and wire41- up to the supplementary switch arm 45 are de-energized but, thecircuit from the electromagnet is maintained across the arm 45, fixedcontact 46 and wire 22 to the thermo-bar 11,

and flexible blade 17, contact 14, wire 16, transformer 42, and Wire 41to the electromagnet 23. The leads from the supply or power I armatureweight 25 drops and, through the lever 27, rocks the lightercounterweight 28 of the switch-arms, moving the latter as Well as theshort arm 45 to'open positions for a subsequent cycle of operations.

This novel process and apparatus forming the subject-matter of thisapplication may be employed in conjunction with the abovethermosstaticcontrol mechanism, which is in present use, as well as with other typesbut, as before stated, for purposes of explanation, it will be describedand its operation pointed out in connection therewith.

The novel safety means featured in this invention and hereinbeforementioned consists of an automatically operable circuit-breakerinterposed in the relay circuit and also a thermostatically controlleddevice adapted to be mounted so as to be responsive to conditions ofcombustion automatically to affect the operation of the circuit-breakerto interrupt the fuel feeding means or burner motor in case of ignitionfailure upon initial starting of the fuel feeding means.

The thermostatically controlled device will next be described and, asshown in Figures 1, 2 and 3, comprises the casing 45 which preferably isopen on one side as shown in Figures 2 and 3. A closure 46 is providedto close the open side of the casing as shown to prevent dust andforeign material from getting thereinto and affecting the operatingmechanism mounted therein. A flanged bracket 47 is secured to the casing45 to provide a means for securing it to a supporting means such, forexample, as the stack 48 of the furnace or heating plant. Athermo-element 49 has one end secured to the bracket 47 and inwardlyprojects into the stack 48 so as to be directly affected by the productsof combustion when ignition takes place. A cap 51 is secured to the endof the thermo-element 49 and has a stem 52 secured thereto which extendsthrough the thermo-element and into the casing 45 as particularly shownin Figure 1. The coefficient of expansion in the thermo-element 49 isobviously considerably greater than that of the stem 52 so that whenignition takes place and the element becomes heated it will relativelyelongate sufficiently to cause the inner end of the stem 52 to be in--wardly drawn towards the wall of the stack. A switch arm 53, having anadjustably mounted contact screw 54 mounted therein, is pivotallymounted-upon a stud 55 mounted in a hub 56 secured to the casing wall asshown in Figure 2 The switch arm 53 has an arm 57 provided thereon whichis connected to the inner end of the stem 52 by means of a pin 58 asshown. The aperture 59 in the stem 52, through which the pin 58 passes,is preferablyplongated so as to permit the stem to relatively move withreference to the arm 57 when the contacts of the device are in circuitclosing position as shown in Figure 1. A tension spring 61 has one endterminally secured to the arm 57 and its other end to the casing wall,thereby constant- .ly exerting a,pull on the arm which tends.

to move the switch arm 53, and therefore the contact 54, into circuitclosing position.

A disc 62 is also mounted upon the stud 55 and is'frictionally preventedfrom relative rotation thereon by means of a tension member 63interposed between the lower face of the hub of the switch arm 53 andthe upper face of the hub 56. (See Figure 2.) A. flexible contact member64, having a contact tip 65 on each side thereof, is mounted -in a stud66 secured to the disc 62 as shown,in Figure 1. A wire 67 electricallyconnects the stud 66 and therefore the contact member 64 with a terminalpost 68 trically connecting the terminal post 68 with a similar terminalpost 69 mounted in the wall of the casing and not insulated therefrom sothat current may pass from the post 68 through the wire 67, flexiblemember 64, contact tip 65, screw 54, switch arm 53, stud and through thecasing wall to the post 69. A third terminal post 71 is also mounted inthe casing wall in insulated relation thereto and is electricallyconnected to a post 72, mounted upon the disc 62, by

means of a flexible connection 73.- A'con-. tact screw 74 is adjustablmounted on the post 72 and is adapted to e engaged by the flexiblecontact member 64 to close a circuit between the terminal posts 68 and71.

An important feature of this invention resides in the construction ofthe novel switchmechanism above described, and in the order in which theswitch contacts 54, and 74 are moved into and out of circuitclosing andcircuit-opening positions by the action of the thermo-element 49 which,as before stated, is directly responsive to conditions of combustion inthe burner. These switch contacts are so arranged that the When thethermocircuit-opening and circuitclosing positions may be varied to anydesired degree. They are also arranged to successively open and closeduring each cycle of operation.

The means provided for controlling the timed relation between theopening and closing of the contacts preferably consists in mounting uponthe disc 62 a pair. of posts and 75 having stop screws 76 and 77,respectively, adjustably mounted therein. The stop screw 76 is adaptedto beterminally engaged by the switch arm 53 when moved into theposition shown in Figure .5. They stop screw 77 has a headed pin 78secured thereto which extends "through an aperture in the flexiblemember 64 so that when the contact-screw 54 is moved out of contact withthe tip 65 of the member 64, as par ticularly shown in Figure 5, themember 64 will engage the head of thepin 78 which will thereby preventits further movement,

thereby allowing the contact screw 54 to be and the other tip 65 on theopposite side of the flexible member 64, may be increased or,

decreased to obtain the desired time interval in the opening and closingof the contacts.

In the operation of the above switch mechanism, it will be noted thatwhen the off-set arm 57 of the switch arm 53 is actuated by the actionof the thermo-element 49 the disc 62 will also tend to rotate upon thestud 55 as a result of the tension member 63 frictionally connecting itwith the hub of the switch arm 53. Such rotation of the disc 62 with thearm 53 will cause the contacts to remain in closed position as a resultof the flexible member 64 and the post 72 being carried by the disc.Means are therefore provided for interrupting the rotation of the discat a predetermined period so thatcontinued rotation of the switch armupon the stud 55 will cause the switch contacts 54, 65 and 74 to besuccessively moved out of contact with one another as shown in Figure 5.The means provided for thus interrupting the rotation of the disc 62pref erably consists of securing a pin 79 to the disc so that it dependstherefrom into the path of a small off-set lever 81 which has one end'pivotally connected to the casing wall by means of a pin 82. Theconnection between the lever 81 and the casing wall is such that it willbe frictionally held in its adjusted positions,

Referring to Figure 1-, it will be noted that 65 time interval requiredto move them into the pin 79 is out of. contact with the lever mama:

81, thereby allowing the disc 62 to rotate with the switch arm 53 untilthe pin engages the lever 81 as shown in Figures 4 and 5. After the pinthus engages the lever 81 rotation of the disc will be interrupted andthe switch arm 53 will continue to move followed by the flexible member64, the tension of which tends to keep it in electrical contact with thecontact screw 54. When the switch arm 53 reaches the osition shown inFigure 4, the flexible mem er will engage the head of the pin 78 and itsmovement will thereafter cease, thereby allowing the contact screw 54 tobe moved out of electrical contact with its complementary tip 65 of themember 64 as shown in Figure 5. Upon the return movement of the switchcontacts, or when they are moved into circuit-closing position b thecooling of the thermo-element 49, the iso 62 will be rotatedsimultaneously with the switch 'arm 53 by the action of the spring 61until the stop pin 79 engages a stop lug 83 mounted in the casing wallas shown in Figures 1 and 3. As soon as the pin 79 thus engages the stoplug 83, the switch contacts will be successively moved into electricalconnection with one another as previously described. By mounting thedisc and switch contacts, as above described, a predetermined clearancewill always be maintained between the contacts when in open orinoperative position, thereby always causin to be presented a preetermined time after i the burner has been interrupted and also be- Jfore the circuit breaker circuit is presented.

Referring to Figure 6, it will be noted that the wire 15 leading fromthe contact 13 of the room thermostat is connected to the terminal post69 of the above described switch mechanism which will hereinafter bereferred to as the combustion thermostat. A wire '84 also leads fromtheterminal 69 to one side of an ignition circuit comprising-the wires 85and 86, the latter being connected by a wire 87 to the secondary of atransformer 88 as shown. The other side of the transformer secondary isconnected to the terminal 68 by means of" a wire 89. The form ofignition means shown in Figure 6 preferably comprises a as valve 91which is automatically operable y means of a relay coil 92 connected inseries with the wires 85 and 86 and therefore the secondary side of thetransformer 88.

A spark coil 93, of ordinary construction, also .has one of its windingsconnected in series, with the transformer 88 through the 001111 bustionthermostat while the high tension winding thereof is connected in serieswith a spark plug 94 as shown. 7 The above described method of ignitionis commonly known as a bustion thermostat. It will also noted that theignition circuit a the primary of the transformer 88 is electricallyconnected to themotor leads 37 and 38 by means of the shunt wires 95 and96, as shown, so that the transformer will be energized whenever themotor switch is closed and the motor is operating.

The circuit-breaker, which is actuated by the action of the combustionthermostat, will next be described, after which the o eration of thesafety means will be describe in connection with. the thermostaticallycontrolled relay circuit controlling the o eration of the burner motorand therefore t e fuel feeding means. The circuit-breaker, shown diaammatically in Figure 6, comprises a con uctor strip 97 secured to aterminal post 98 to which i 16 which leads from the post 14 of the roomthermostat to the transformer 42 so that the normal engagement of theswitch arm 99 with the conductor strip 97 of the circuit breaker doesnot interrupt the thermostatically controlled circuit at the Wire 16. 1

The means rovided for automatically moving the swltch arm 99 out ofcontact with the conductor strip 97 to break the circuit, in case ofignition failure, preferably consists of a thermo-bar 104 having oneendsecured to a support 105 secured to thesupporting strip 102. The outeror free end of the 'thermo-bar, has a reduced portion forming a tab 106which is adapted normally to be received within an angular recessprovided in the depending off-set end 107 of the movable switch arm 99of the circuit breaker. A heating coil 108 is coiled about thethermo-bar and has one end connected by a wire 109 to the w' e 89leading to one side of the vsecondary oifthe transformer 88. The otherend of the heating coil is similarly connectedby a wire 111 tothe wire41 leading fromtheintermediate contact post 71 of the combustionthermostat to the post 34 of the ,motor switch. The circuit-breaker isso constructed and arranged that, upon the passage of current throughthe heating coil 108 for a predetermined interval, the vthermmbar 104will be warped out o'f engagement with the off-set end 107 of themovable switch arm99, which is mounted sothat its inherent resiliencewill cause the ,arm99 toassume the position shown in dotted. lines inFigure 6 with the result that the switch arm 99 is moved out of contact6 means ergized and the motor circuit is broken at the switch contacts31. The apparatus can thereafter only be re-conditioned for normaloperation by the manual re-setting of the circuit-breaker switch and 99,such, for example, as by a push button 112, preferably mounted in thesupporting strip 102 of the circuit-breaker.

In the operation of this novel safety means in connection with thethermostatically controlled relay circuit of the burner motor and fuelfeeding means, the apparatus, after a predetermined room temperature isreached, will be in the position shown in Figure 6, wherein it will benoted that the contact blades 12 and 17 of the room thermostat are outof electrical contact with the posts 13 and 14. When thus positioned thecircuit through wire 16 of the relay will be broken at the roomthermostat thereby causing the electromagnet 23 to become de-energized,which will cause the motor switch vto be automatically opened by thegravita- When the contacts of the combustion. thermostat are thusclosed, the wire 41 of the relay circuit will be electrically connectedto the wire 15 leading to the room thermostat so that current may flowfrom the electro magnet 23 through the wire 41, combustion thermostat,wire 15 to the post 13 of'the room thermostat where it will beinterrupted until the tip 18 of the blade 12 is moved into contact withthe contact screw 13. It will also be'noted that when the contacts ofthe combustion thermostat are in closed position, that the heating coil108 and also the igni tion means will be connected in series with thesecondary of the transformer 88 so that when the burner motor resumesoperation by the automatic 'closing of the motor switch by the action ofthe room thermostat that ignition will also be simultaneously resumed.

As 'soon as the room temperature begins to lower the'contacts 18 of theblades '12 and 17 of the room thermostat will move towards the contactscrews 13 and 14 until the tip 18 of the blade 17 is moved intoelectrical connectionwith the contact 14. Such connection, however; w1llhave no effect on the apparatus as a result of the blade 12 being out ofcontact with the contact 13, and also as a result of theseparatedrelations of contact 46 and the blade 45. Further cooling of the roomwill cause the tips 18'of the blade 12 to be moved into electricalconnection with the contact screw 13 thereby completing or closing therelay circuit which will be-as follows :-From the secondary of thetransformer 42 through the wire 16 and circuit breaker interposedtherein, contact screw 14, blade 17, contact screw 13, wire 15, to theterminal post 69 of the combustion thermostat; through the casing of thelatter to the contact screw 54, tips 65 of the switch member 64, post72, connection 73 to the intermediate terminal post 71;

thence through the Wire 41 to the electromagnet 23 and back to the otherside.of the transformer secondary. Closing of the above circuit willcause the electromagnet 23 to become energized resulting in the armature24 being upwardly drawn thereby resulting in the weight 28 dropping andautomatically clos ing the switch arms 29. Such closing of the motorswitch will cause the motor 7 and the ignition means to resume operationwith the resultant operation of burner under normal conditions. As soonas combustion has thus been started, the heat of combustion will affectthe thermo-element 49 causing it to elongate and thereby actuating theswitch mechanism. mounted in the combustion thermostat. The firstmovement of the thermo-element 49 upon combustion resumption will causeone of the tips 65 of the blade 64 to be moved out of electrical contactwith the contact screw 74 as shown in Figure 4, thereby breaking 41 atthe combustion thermostat will also and circuit-breakerto the contactscrew 14 of the room thermostat; thence through the blade 17, coiledthermo-bar 11, wire 22, contact 46, switch arm 45, wire 41 to theelectromagnet2 3 and thence back to the other side of the transformer42.

Referring further to the operation of the combustion thermostat, aftercombustion has been resumed and the circuit-breaker circuit has beenopened, as above described, the contact screw 54 of the switch arm 53will be interrupting the ignition means which condi- 7 tion will obtainuntil the room temperature rises and the electromagnet circuit is brokenthrough the room thermostat, after which the entire apparatus will berendered inoperative and combustion will cease. Upon such interruptionof combustion the thermo-elementv 49 of the combustion thermostat willbegin to cool, and first present or close the resumption thereof whenthe burner is normally running and the room thermostat is in electricalcontact with the contact screws 13 and 14, it will be impossible for theburner to resume operation until after the' thermoelement 49 of thecombustion thermostat has cooled sufliciently to present or close theignition'circuit before the electromagnet becomes energized to close themotor switch. This is accomplished by the timed relation of the openingand closing of the switch contacts in the stack thermostat which are soarranged that the ignition circuit is always closed before the motor orpower feeding means is started after having been accidentallyinterrupted. p

In the event of ignition failure when the fuel feeding means is startedby the closing of the main motor switch by the indirect action of theelectromagnet 23 and the room thermostat, the thermo-element of thecombustion thermostat will not become heated, thereby causing the,contacts 54, and 74 thereof to remain in circuit-closing position sothat current will flow through the heating coil 108 which will cause thethermo-bar 104 to warp and be moved out of contact with the off-set endportion 107, thereby causing the switch arm 99 to be moved out of;electrical contact with the conductor strip 97 and thus opening therelay circuit with theresultant opening of the motor switch andtherefore interruption ofthe fuel feeding means. After thecircuit-breaker has thus opened the wire 16 the apparatus can only bere-conditioned or rendered operative again by the manipulation of thepush button 112 to re-se't the switch arm 99 in circuit-closingposition. It is also to be understood that the time required to open thecircuit-breaker by the flow of current through the heating coil 108 isgreater than that required by the thermo-element 49 of the combustionthermostat to open the circuit-breaker circuit torender it inoperative,so that upon normal operation of the burner the circuit-breaker willalways remain in closed position. The initial starting operation of theburner ignition under normal conditions will be started simultaneouslwith the starting of the motor or fuel-fee ing means, and at thesametime current will be caused to flow through the heating coil 108. of thecircuit breaker which circuit, however, will soon thereafter be openedthrough the combustion thermostat after combustion is started, afterwhich ignition will subsequently be interrupted and the burner willcontinue to function until interrupted by the action of the roomthermostat.

Having thus described my invention what I claim as new and desire tosecure by Letters- Patent is: V

1. A thermostatically operable device for opening and closing electriccircuits, comprising in combination a thermo-element and a supportingmeans therefor, a contact movably mounted upon said supporting means andhaving a connection with said thermoelement, a rotatable disk, aflexible contact member mounted upon said disk and adapted to be engagedby said movable contact, a complementary contact also mounted upon thedisk adapted to be engaged by said flexible contact member whereby uponactuation of said movable contact by the thermo-element, all of saidcontacts will be successively moved into and out of electrical contactwith one another.

2. A pair ofelements mounted to move independently one having a pair ofcontacts against which the other element operates so that one elementcan alternately move the other in opposite directions, a thermal deviceconnected to moveone of the elements.

3. A. pair of elements mounted to move in dependently one having a pairof contacts, against which theother element operates so that one elementcan alternately move the element which. is not. connected with saidthermal device along with additional means ,switch arm operative betweenone of the pair of contacts and that element which operates between thecontacts, and a third contact engageable with said arm to limit itsmovement toward the element when said element recedes therefrom towardthe opposite contact of the pair, the arrangement being such that whenthe element is engaging that opposite contact,

the switch arm is in circuit making condition only with the thirdcontact.

6. A pair of elements mounted to move independently one having a pair ofcontacts against which the other element operates so that one elementcan alternately move the other in opposite directions, a thermal deviceconnected to move one of the elements, means for limiting movementsalternately in opposite directions of that element which is notconnected with said thermal device, a switch arm operative between oneof the pair of contacts and that element which operates between thecontacts, and a third contact engageable with said arm to limit itsmovement toward the element when said element recedes therefrom towardthe opposite contact of the pair,'the arrangement being such that whenthe element is engaging that opposite contact, the switch arm is incircuit making condition only with the third contact.

7. A pair of elements mounted to move independently one having a pair ofcontacts against which the other element operates so that one elementcan alternately move the other in opposite directions, a thermal deviceconnected to move one of the elements, means 4 for yieldably retardingthe motion of that element which is not connected with said thermaldevice, a switch arm operative between one of the pair of contacts andthat element which operates between the contadts, and a third contactengageable with said arm to limit its movement toward the element whenthe element recedes therefrom toward the op-' posite contact of thepair, the arrangement being such that when the element is engaging thatopposite contact, the switch arm is in mounted and swingable against thecontacts and a thermal element arranged to swing the arm, and having alost motion connection therewith, and means yieldably urging said armtowards one of the contacts.

. .10. A support rotatably mounted and yieldabl'y retarded againstrotation and having a pair of contacts, an arm independently mounted andswingable against the contacts and a'thermal element arranged to swingthe.

arm and having alost-motion connectiontherewith, means yieldably urgingsaid arm towards one of the contacts, said thermal ele- .ment moving inone direction against the action of said yieldable means to draw ittoward an opposite contact, and means to limit movement of the supportin opposite directions when said arm is correspondingly moved by thethermostatic element and when in engagement with a contact.

In witness whereof, I have hereunto set my hand this 24th day of June,1925.

FREDERICK S. DENISON.

